These replace vouchers issued previously, which must now be destroyed in the presence of a witness.

Details of how to use the new vouchers and destroy the old ones are set out in guidance sent out by the DoH.

The new vouchers are being issued to reflect changes to recommended doses of oseltamivir (Tamiflu) and the fact that annotated FP10 forms should not be used to authorise antivirals for children.

There are now three types of voucher: green for children under six months old, red for children aged six months to a year and orange for patients over a year old.

The vouchers must be used to authorise provision of antiviral medicines for children under the age of 13 (annotated FP10s cannot be used for these patients).

Specially-endorsed FP10 forms should be used to authorise antivirals for patients aged over 13, unless the GP computer system cannot be used for any reason.

The vouchers are only for use in England and are being sent directly to GP practices, health centres and out-of-hours services. They should begin to be used as soon as they are received, the DoH has said.